I promised to show you another apron that uses rickrack creatively and here it is. The technique for attaching the rickrack can be used on anything—not just gingham—but this example shows a nice use of cross stitches in between the rows. And it's another idea for trimming your gingham apron if you're doing one for the challenge.
Use colored embroidery floss (same color as the gingham) across the dips in the "waves" to attach your rickrack to the fabric. Running your stitches all in the same direction gives you a striped effect; alternating direction forms a v-shaped design.
The apron shown here has the rickrack along the waistband and pocket tops—one row of the larger size in the center surrounded by two rows of the smaller size. Along the bottom are two rows of this same arrangement with the addition of cross stitches on the white squares in between. Looks pretty fancy but isn't quite as much work as chicken scratch!